ST. LOUIS (AP) — A Ferguson city councilman and former mayor who was the driving force behind the “I Love Ferguson” campaign that began amid the turmoil that followed the fatal police shooting of 18-year-old Michael Brown has died.

City officials confirmed that 56-year-old Brian Fletcher died Sunday, but say the cause of death is unknown.  Fletcher served as mayor from 2005 to 2011, then returned to politics with his election to the council in April.

Brown, who was black and unarmed, was killed by Ferguson officer Darren Wilson during a street confrontation on Aug. 9, 2014. A St. Louis County grand jury and the U.S. Department of Justice declined to prosecute, but the shooting led to sometimes-violent protests. Fletcher and others began the “I Love Ferguson” campaign soon after the shooting.